Release v0.8.1

Fixed

• Volcengine voice transcription now deletes the temporary TOS object after ASR completes, preventing staged voice files from accumulating over time
• TOS cleanup failures are isolated to logs and no longer affect user-facing transcription replies

Changed

• Extended TOS uploader API to return uploaded object metadata (object_key + signed URL) for explicit post-transcription cleanup
• Added tests covering TOS object deletion on both success and failure paths